The present invention relates to the art of making filamentary material by rotating a heat-extracting member in contact with a source of molten material and solidifying a portion of the molten material as a filamentary product on the surface of the rotating member from where it spontaneously releases and is subsequently collected.
The present invention is an improvement over the methods disclosed in U.S. Pat. No. 3,838,185 (Maringer, et al) and U.S. Pat. No. 3,896,203 (Maringer, et al), both assigned to common assignee, Battelle Development Corporation, and said patents are incorporated herein by reference to the extent necessary for a full and complete understanding of the present invention.
The prior art is replete with methods and apparatus disposed to produce filamentary material directly from a source of molten material. Many prior art methods are limited to metal products and most use some type of forming orifice to control the size of the filament. Typical of such teachings is U.S. Pat. No. 2,825,108, Pond, where the molten material (a metal) is formed into a filamentary form by forcing it through an orifice so as to form a free standing stream of molten material which is subsequently solidified into filamentary form on a rotating heat-extracting member. The rate of production is determined by the rate at which the molten material is expelled from the orifice and for continuous filament this rate must be at least roughly synchronous with the rate of movement of the heat-extracting member at the point of impingement. Techniques of this type are troubled by the relative complexity of process control and the inherent difficulty in passing molten material through small orifices. The orifices must be of an exotic material if the molten material has a relatively high melting point and the orifices have a tendency to erode or clog. A successful solution to the problems arising with forming orifices is taught in U.S. Pat. No. 3,838,185, where a disk-like heat-extracting member forms the filamentary product by solidifying the product on the outer edge of the disk as it rotates in contact with the surface of a pool-like source of molten material. In this manner a filamentary product is formed without the use of a forming orifice. This teaching, however, is limited to the use of a pool-like source of molten material. Such a source of molten material necessitates the melting and holding of significant quantities of material. While the amount of heat needed to melt a given mass of a solid is the same regardless of its future disposition, the holding of quantities of molten material introduces several problems. The first is simply the energy required to maintain the molten material at high temperature. Second is the exposure of the molten material to the atmosphere. Without isolating the pool-like source of molten material from the atmosphere, it is difficult to maintain constant chemical compositions in the molten material due to oxidation at the surface of the melt or the loss of volatile materials from the melt.
A successful solution to these problems is taught by U.S. Pat. No. 3,896,203, where the source of molten material is a portion of molten material adherent in a drop-like form to a solid with its shape determined by the surface tension of the molten material. The circumferential edge of a rotary disk-like heat-extracting member is brought into contact with the molten material and a filamentary product is formed adherent to the rotating member. Ultimately, the filament spontaneously separates from the rotary member to be collected. This teaching, however, does not indicate any solution to problems of collection. Further, this teaching permits centrifugal force to assist in removing the casting from the surface of the rotating disk, thus shortening the time of contact and decreasing the amount of heat which can be transferred from the solidifying metal to the rotary disk.
The present invention utilizes centrifugal force to maintain contact of the cast filamentary product with the rotating disk thereby increasing the amount of heat transfer and increasing the quench rate.
A further advantage of the present invention is that the cast filament can be guided directly into a cylindrical cavity which is an integral part of the casting system, thus causing the cast filament to be collected with a minimum amount of disturbance to its natural trajectory.
The present invention finds significant utility in forming filamentary products for which very high quench rates are required, and in providing for the collection of those filaments in convenient coils.